title: Arginine/lysine residues in the cytoplasmic tail promote ER export of plant glycosylation enzymes.
abstract: Plant N-glycan processing enzymes are arranged along the early secretory pathway, forming an assembly line to facilitate the step-by-step modification of oligosaccharides on glycoproteins. Thus, these enzymes provide excellent tools to study signals and mechanisms, promoting their localization and retention in the endoplasmic reticulum (ER) and Golgi apparatus. Herein, we focused on a detailed investigation of amino acid sequence motifs present in their short cytoplasmic tails in respect to ER export. Using site-directed mutagenesis, we determined that single arginine/lysine residues within the cytoplasmic tail are sufficient to promote rapid Golgi targeting of Golgi-resident N-acetylglucosaminyltransferase I (GnTI) and alpha-mannosidase II (GMII). Furthermore, we reveal that an intact ER export motif is essential for proper in vivo function of GnTI. Coexpression studies with Sar1p provided evidence for COPII-dependent transport of GnTI to the Golgi. Our data provide evidence that efficient ER export of Golgi-resident plant N-glycan processing enzymes occurs through a selective mechanism based on recognition of single basic amino acids present in their cytoplasmic tails.
authors.affiliation: Department of Applied Plant Sciences and Plant Biotechnology, Institute of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences, BOKU-Vienna, Muthgasse 18, Vienna, Austria.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Schoberer
authors.forename: Ulrike
authors.initials: U
authors.lastname: Vavra
authors.forename: Johannes
authors.initials: J
authors.lastname: Stadlmann
authors.forename: Chris
authors.initials: C
authors.lastname: Hawes
authors.forename: Lukas
authors.initials: L
authors.lastname: Mach
authors.forename: Herta
authors.initials: H
authors.lastname: Steinkellner
authors.forename: Richard
authors.initials: R
authors.lastname: Strasser
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000201:enzymology*; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000201:enzymology; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D008361:Mannosidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D001120:Arginine; D017351:N-Acetylglucosaminyltransferases; C024850:alpha-1,3-mannosyl-glycoprotein beta-1,2-N-acetylglucosaminyltransferase I; D008361:Mannosidases; C038829:mannosyl-oligosaccharide 1,3 - 1,6-alpha-mannosidase; D008239:Lysine